Power consumption has become an important issue in the automotive industry. Recently, a greater emphasis has been placed on extending the life span of car batteries. Power drainage is a particular problem in colder climates where vehicles are parked for long periods of time, thereby significantly reducing the available battery power as a result of the temperature. This presents a unique dilemma when taken in combination with the increasing electrical and electronic content and complexity within present automobiles.
One solution for reducing overall power consumption has been to place specific power consuming electronic components, such as a microcontroller, into a sleep mode of operation for periods of inactivity, and an active mode of operation when external activity is detected. By such an arrangement, these components draw a minimal quiescent current from the battery during the sleep mode operation up until such time as the system requires them to be fully operational.
In order to design a remote control system having a microcontroller with a sleep and an awake mode of operation employing the above power consumption savings solution, a switch is inherently required to facilitate the transfer between operational states. In cases where a remote control system is utilizing such a scheme, the switch may be triggered by an external message. This external "wake up" message is initially received by the receiver to enable the microcontroller to change states from the sleep mode to the awake mode of operation.
Several "wake up" message schemes have been proposed for the above design scenario for controlling the switching mechanism to enable the microcontroller to switch between operational states. In one known approach, a "wake up" indicator is appended to the actual data message which is transmitted as a signal and received accordingly. Here, a series of wake up pulses are employed as the "wake up" indicator.
However, this known "wake up" indicator technique has several shortcomings. Firstly, the wake up pulses become difficult to detect by the receiver in the presence of ambient noise. Similarly, with signals also being transmitted by other devices, reception as well as detection may falsely trigger the receiver. Moreover, this known approach is relatively expensive, requiring several individual components, while providing an acceptable power savings.
As such, there remains a need for a wake up detector that has a greater immunity to ambient noise. Furthermore, a demand exists for a wake up detector which reduces the likelihood of false triggers. A need also exists for a wake up detector which is less costly to manufacture while having improved power savings.